[puddleglum]

I'm not the best person to give advice on an electric drive because I haven't done one yet, but I know a little of how they work. Regarding direct drive, this simply refers to how the motor is connected to the wheels, not how the motor is controlled. The controller varies voltage and current to the motor based on throttle input to control speed. At zero throttle the motor is in neutral and freewheels. Since most electric motors make peak torque at zero rpm, the trans is not a necessity. You will need to get the motor size and gearing just right, though, if you want good acceleration and high speed performance.
If you want to be able to do 140 miles at 65 mph, you will need a large (read expensive and heavy) battery pack and you would need to go lithium. How big is this trike you are planning? If it's based on a 250, I'm guessing not very big. If you built a super aerodynamic shell for it, it would cut your power need but adds to the complexity and expense of the project. Your budget may dictate your design choices as much as power requirements. It's nice to see you're starting young though. Here is another link to some good info. EV Information - DIY Electric Car Forums